Preventing Cancer in the Womb

By AMY DOCKSER MARCUS
Staff Reporter of THE WALL STREET JOURNAL
November 2, 2004; Page D1

Add this to the list of things expectant mothers need to worry about: New research suggests that what and how much a mother eats while pregnant could increase her child's risk of getting cancer later in life.

It has long been known that what a mother eats and drinks during pregnancy has an effect on a child's long-term health -- with studies linking alcohol and smoking to mental and physical development, and even connecting low birth weight to heart disease in adulthood. But researchers are now seeing indications that a mother's diet and weight gain could affect cancer risk specifically.

THE PRENATAL DIET What are your thoughts the new research? Join a discussion with Journal reporter Amy Dockser Marcus about prenatal nutrition.

While little is known about the effect of specific foods eaten by the mother, the emerging evidence about the implications of birth weight is compelling. Babies who weigh more than 8.8 pounds at birth -- or who are at the 90th percentile or higher for weight for babies born the same gestational week of the pregnancy -- are at greater risk of getting breast cancer, prostate cancer and testicular cancer as adults, according to a number of recently published studies.

Data from a large study published earlier this year of children born in Jerusalem from 1964 to 1976 show that higher birth weight also appears to be associated with an increased risk of acute myeloid leukemia in infants, children and young adults. More needs to be known about whether there are differences if a baby is relatively large because the parents are tall people or because the mother gained a lot of weight. But because weight gain is controllable and height isn't, researchers have focused on the mother's diet.

In addition, a number of animal studies suggest high-fat diets in the mother can lead to an increased risk of breast cancer in female offspring. The research is continuing with several new studies being launched this year.

To date, efforts to prevent cancer have largely focused on people who are known to be at higher risk due to genetic mutations they inherit from their parents. But the current research has more wide-ranging implications because it potentially applies to anyone, not just those who have a family history of cancer.

The results of the studies have led cancer researchers to argue that more attention needs to be paid to what women eat when they are pregnant, including being more aggressive about urging women not to gain more than the recommended 15-25 pounds during pregnancy. Doctors say women are increasingly gaining too much weight during pregnancy. In 2002, the most recent year for which figures are available, 21.2% of women had a weight gain of over 40 pounds during pregnancy, according to the Centers for Disease Control and Prevention, and that number has been rising since data were first collected in 1989.

All this puts further pressure on pregnant women, who are already struggling to follow a growing list of recommendations of what to eat. "You don't want to drive women crazy," says Karin B. Michels, an associate professor at Harvard Medical School and co-author of a book of recipes for pregnant women interested in lowering their children's risk of health problems as adults. She acknowledges that women may feel guilty if they can't keep up with the book's suggestions, like cheesy mushroom omelets and whole wheat toast for breakfast, snacks like papaya and roasted pumpkin seeds, and dinners of ginger-seared Chilean sea bass, vegetarian chili or salmon.

Controlling Weight Gain

Until more is known, Dr. Michels advises pregnant women to eat foods that will maximize nutrition and help control weight gain, including increased amounts of fresh fruits and vegetables, whole grains like brown rice and quinoa, and beans, lentils, and chickpeas -- to create what she calls "a more optimal growth environment" for the baby.

TIPPING THE SCALES In several studies, a relatively high weight at birth has been linked to increased risk for these cancers later in life: • Breast cancer in adults   • Prostate cancer in adults   • Testicular cancer in adults   • Acute myeloid leukemia in infants, children and young adults   THE PRENATAL DIET One theory of a link between prenatal diet and cancer is that a fetus may be exposed to excessive amounts of growth hormones the mother gains too much weight. Thus the focus has been on controlling the mother's weight and maximizing her nutrition. • Increase intake of fresh fruits and vegetables.   • Eat more whole-grain products, such as wholegrain bread, brown rice, quinoa.   • Look for sugar-free and natural-grain breakfast cereals.   • Increase intake of nuts, which are high in plant protein.   • Cook using vegetable oils like canola oil and olive oil.   • Eat more beans, lentils, peas, chickpeas.   • Avoid refined grains and sugars.   Sources: Karin B. Michels, and "The Gift of Health" by Dr. Michels and Kristine Napier

Just how a mother's diet and weight gain may affect cancer risk isn't fully understood. One theory is that if a mother gains too much weight, a fetus may be exposed to excessive amounts of growth hormones at a time when cells are dividing rapidly. Large weight gain can also -- though not always -- lead to a larger fetus, with even more cells that could be subject to mutations.

The difficulties of establishing a connection between events that may happen in the womb and cancer risk as an adult are numerous. Cancer is far less common than, say, cardiovascular disease, and researchers require large numbers of people to study in order to make strong connections. Since cancer generally doesn't occur until much later in life, the time between the woman's pregnancy and the adult child's cancer can be six or more decades. The mothers at this point often cannot remember what they ate when they were pregnant.

But several new studies being launched this year may provide further clues. Mary Beth Terry, an assistant professor of epidemiology at Columbia University's Mailman School of Public Health is interviewing 250 men and women in their early 40s whose mothers participated in a pregnancy study done in New York and California in the 1950s and 1960s. Researchers are interviewing the offspring to determine cancer incidence, and then going back to the mothers' blood samples that were part of the original study to measure hormone levels. The idea is to see what growth hormones, if any, might be linked to cancer risk in the children.

Looking Back

L.H. Lumey, a professor of epidemiology at Columbia's Mailman School, has been following 1,000 men and women born in three hospitals in Amsterdam, Rotterdam and Leiden during the Dutch famine in 1944-1945. Researchers are studying the health differences between children born during the famine and those born before or after it, including examining annual mammograms of the female children to measure their level of breast density and look for differences among women born to mothers who had different nutritional circumstances. Women with dense tissue have a statistically higher chance of developing breast cancer later in life.

Dr. Michels at Harvard Medical School says that while there is still not enough information to "design the absolutely perfect diet," she believes the current research demonstrates that "what a woman eats is important to her child's future health more than we previously understood."

In an effort to find connections to specific foods eaten during pregnancy, Dr. Michels is interviewing the mothers of women participating in the Nurses' Health Study, a large national study of registered nurses set up to investigate the possible long-term health consequences of using oral contraceptives. She has asked the mothers to dig out baby books and other written records related to the pregnancy and birth of their child in an effort to link a mother's nutrition and her child's later cancer risk.

Some animal studies are revealing a link between specific foods and the offspring's cancer risk, and this research is being closely followed to see what parallels may exist for humans.

Leena Hilakivi-Clarke, a professor of oncology at Georgetown University Medical Center in Washington, D.C., says that in her study, rats fed a diet of 39% fat -- similar to the typical human diet -- had more offspring that got cancer than rats who had a 16%- to 19%-fat diet. The high-fat rats were fed corn oil, which increases levels of the hormone estradiol. Researchers speculate that the offspring of rats on the high-fat diet were exposed to higher estradiol levels in the womb at a time when the breast cells were rapidly dividing, which resulted in the development of more mammary-gland cells that are at higher risk of becoming cancerous later in life.

Benefits of Whole Wheat?

In other studies, rats fed increased quantities of flax seed had female offspring at greater risk of getting breast cancer. Rats that ate higher levels of whole wheat had female offspring at lower risk of breast cancer. Rats are often used in such studies because of the similarity between the rat mammary gland and the human mammary gland.

Write to Amy Dockser Marcus at amy.marcus@wsj.com

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